Dynamics of Phonon and fluctuation probed by time-resolved resonant x-ray scattering

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03534
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tokyo Institute of Technology (2019-2022); The University of Tokyo (2018)
• Principal Investigator: Takubo Kou 東京工業大学, 理学院, 特任助教 (30738365)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 光誘起ダイナミクス

Outline of Final Research Achievements

We have studied an orbital fluctuation dynamics of transition-metal oxide Ba3CuSb2O9 by means of time-resolved resonant soft x-ray scattering. A pre-edge structure originating from oxygen holes is observed at the pre-edge region of the O 1s edge of the x-ray absorption for the hexagonal Ba3CuSb2O9, which realizes the quantum spin and orbital liquid state. Furthermore, a coherent oscillation with a relatively long period around 6 GHz is observed on the photoinduced dynamics of the soft x-ray resonant scattering at the Cu L3 edge, while this coherent oscillation is not realized on the orthorhombic sample that contain a static Jahn-Teller distortion in the Cu sites. These results indicate the presence of oxygen holes in the sample closely relates the quantum spin-orbital entanglement liquid state and can be controlled optical excitation.

Free Research Field

固体物理

Academic Significance and Societal Importance of the Research Achievements

一般の遷移金属化合物の単一サイトの光学フォノンモードはフェムト秒のオーダーであるため、今までのピコ秒領域の時間分解能のX線散乱などの測定では、コヒーレント振動がほとんど観測されることがなかった。量子スピン軌道液体状態が低温で実現するBa3CuSb2O9は複数のCuサイトの自由度が競合する系であり、放射光X線を用いた時間分解型の共鳴軟X線散乱のダイナミクス測定という最先端の手法を用いて、その軌道-スピン揺らぎの状態と密接に関連する数10ps領域のコヒーレントフォノンを観測することに初めて成功した。